Field
Embodiments of the present disclosure generally relate to a thermal processing of substrates. More specifically, embodiments described herein relate to apparatus and methods for soak annealing.
Description of the Related Art
Heating apparatus are often used in the semiconductor industry for processing substrates. In general, there are typically two broad configurations of heating apparatus. The first is a batch system in which multiple substrates (e.g. 25-200 substrates) are loaded into a tubular furnace and slowly heated to a desired temperature. Batch systems can be considered temperature equilibrium devices in that the furnace walls are approximately at the same temperature as the heating elements and the substrates being heated. Batch systems are typically referred to as “hot wall” systems since the furnace walls are at an elevated temperature. The primary advantage of a batch system is the ability to process many substrates at the same time which results in a cost per substrate reduction. However, batch systems suffer from several disadvantages, one of which is the speed with which the substrate temperature can be elevated or lowered. The large thermal mass of a batch furnace prevents quick temperature changes and leads to relatively long process times, ranging from about 15 minutes to several hours or more.
A second configuration is rapid thermal processing (RTP) where a single substrate is heated in a small process volume using radiant energy as the energy source. For example, RTP systems typically include a substrate support for holding a substrate and a light source than emits light energy for heating the substrate. During heat treatment, the substrate is heated under controlled conditions according to a desired temperature regime.
RTP systems typically operate in a non-equilibrium state. The walls of the chamber are typically cooled with respect to the heated substrate and may be referred to as “cold wall” systems. An advantage of RTP systems is the ability to quickly change substrate temperature which enables short heating cycles which can be between one second and several minutes. However, one drawback of RTP systems is the cost per substrate processed, since the systems are equipped for processing a single substrate at a time.
Accordingly, there is a need in the art for improved substrate annealing apparatus.